Fuel injection nozzle units

ABSTRACT

A liquid fuel injection nozzle unit comprises a valve member movable by fuel under pressure to permit fuel flow through an outlet, a spring acting to urge the valve member to prevent flow of fuel and a fluid pressure operable piston connected to the valve member subjected to a pressure of fuel which creates a force acting to assist the closure of the valve member. The fuel under pressure is obtained from the fuel which leaks past the valve member.

United States Patent 1 1 1 1 3,796,379 I Fenne Mar. 12, 1974 FUEL INJECTION NOZZLE UNITS 3,680,782 13/1972 Monpetit a a1. 239/533 x [75] Inventor: Ivor Fenne, Middlesex, England FOREIGN PATENTS OR APPLICATIONS [73] Assignee: C.A.V. Limited, Birmingham, 1,242,368 8/1960 France 239/533 England Primary Examiner-M. Henson Wood, Jr.

[22] Flled: 1972 Assistant Examiner-Michael Y. Mar

[21] A p], N 300,318 Attorney, Agent, or Firm-Holman & Stern [30] Foreign Application Priority Data [57] ABSTRACT Oct. 30, 1971 Great Britain 50534/71 A liquid fuel injection nozzle unit comprises a valve member movable by fuel under pressure to permit fuel 52 US. Cl. 239/533 flow throueh an Outlet, 3 Spring acting to urge the 51 rm. c1. F02m 47/00 valve member to Prevent flow of fuel and a fluid p [58] Field of Search 239/94, 96, 533 Sure Operable Piston Connected to the valve member subjected to a pressure of fuel which creates a force 5 References Cited acting to assist the closure of the valve member. The

fuel under pressure is obtained from the fuel which UNITED STATES PATENTS leaks past the valve member.

3,610,529 10/1971 Huber 239/533 X 3,688,986 9/1972 Guegan et al 239/533 X 10 Claims, 1 Drawing Figure 1 FUEL INJECTION NOZZLE um'rs This invention relates to liquid fuel injection nozzle units of the kind comprising a valve member movable in a bore under the action of fuel under pressure, said valve member being shaped for cooperation with a seating whereby when the valve member is moved by the action of the fuel under pressure, fuel can flow through an outlet and resilient means for urging the valve member into contact with the seating.

The object of the invention is to provide such a nozzle unit in a simple and convenient form.

According to the invention a fuel injection nozzle unit of the kind specified comprises a fluid pressure operable means and a conduit through which fuel under pressure leaking between the valve member and the bore is applied to said means, said means being coupled to the valve member so that the fuel under pressure assists the action of the resilient means in closing the valve member onto the seating.

One example of a fuel injection nozzle in accordance with the invention will now be described with reference to the accompanying drawing which shows in diagrammatic form three such nozzle units coupled together and for supplying fuel to a multi cylinder internal combustion engine.

Referring to the drawing each nozzle unit includes a nozzle body 10 having at one end a right cylindrical screw threaded projection 11 against the end face of which is located a nozzle head 12. The nozzle head is retained relative to the projection 11 by means of a screw threaded cap nut 13. Formed within the nozzle head is an axially extending bore in which is located a slidable valve member 14 and the end of the valve member is shaped for co-operation with a seating.

Formed in the body part 10 is a fuel inlet 15 which communicates with a fuel gallery 16 formed in the nozzle head and from which extends an outlet, the aforesaid seating being defined about the outlet. The nozzle unit thus far described is well known and the arrangement is such that when fuel under pressure from a pump 30 is admitted through the inlet 15, the pressure of fuel acting on the valve member 14 will move the valve member away from the seating thereby to permit flow of fuel to the outlet.

Formed within the body part is a cylinder 17 in which is slidable a piston 18 having a flange adjacent its end remote from the valve member 14. The flange serves as an abutment for a coiled compression spring 19 which is located within a chamber 20 which forms a continuation of the cylinder 17. The end of the cylinder remote from the piston forms an abutment for the spring.

The other end of the cylinder 17 is closed apart from an aperture through which extends a push rod 21. The push rod at one end bears against the valve member 14 and at its other end against the piston 18. The main portion of the push rod 21 is accommodated within an elongated recess 22 which communicates with the bore in which the valve member 14 is mounted and the recess 22 also communicates with the chamber 20 by way of a conduit 23.

In the arrangement shown in the drawing three such nozzle units are provided and the chambers 20 of the nozzle units are interconnected and the pressure therein is controlled by a control valve 24. This valve includes a spring loaded valve element 25 which is slidable within a cylinder, one end of which communicates with the chambers 20 and the other end of which communicates with a drain. A step is defined in the cylinder and the valve member is provided with a peripheral groove which is open to the end of the cylinder communicating with the chambers 20. The arrangement is such that with increasing pressure within the chambers 20, the valve member 25 moves against the action of its resilient loading and controls the pressure within the chambers 20 by allowing fuel to spill therefrom.

In operation, fuel under pressure leaking along the working clearance defined between the valve member 14 and the surface of its associated bore flows by way of the conduit 23 into the associated chamber 20. This fuel under pressure acts on the end surface of the piston l8 and also on the portion of the end face of the valve member 14 remote from the seating 16 and not covered by the rod 21 and thereby assists the action of the spring 19 in moving the valve member 14 into contact with the seating. As mentioned above the pressure which can exist in the chamber or chambers 20 is controlled by the control valve 24.

When the engine is at rest the pressure within the chambers 20 is zero so that when the engine is started the resistance offered to movement of the valve members 14 is due only to the respective springs. However, as the pressure within the chambers 20 increases the force acting on the pistons increases and this effectively increases the forces exerted by the springs 19. This improves the performance at high speeds and it overcomes the disadvantage which would result by merely increasing the force exerted by the spring 19, that is to say the difficulty in ensuring that sufficient pressure is available at the fuel inlet 15 when the engine is started.

As shown in the drawing the chambers between the closed ends of the cylinder 17 and the respective pistons 18 are connected to the aforesaid drain by way of conduits 26. Each of these conduits incorporates a restrictor 27 the action of which is to restrict the rate at which fuel can flow into the closed end of the cylinder 17 during opening of the nozzle and to restrict the rate at which it flows out of this cylinder when the valve member 14 is closing. If desired the restrictor may have a non-return valve disposed in parallel therewith, the non-return valve being arranged so that substantially no restriction is offered to the flow of fluid into the cylinder 17 during the opening of the valve member 14.

By controlling the rate of flow of fuel out of the cylinder 17 during closure, the final closing velocity of the valve can be controlled and excessive loadings on the valve seat minimized.

It will be appreciated that by coupling the chambers 20 together in the manner indicated the variations in the nozzle opening pressures caused by various factors other than spring pressure, are substantially minimised.

In an alternative construction the piston 18 is replaced by a diaphragm however, the mode of operation of the nozzle unit when so fitted is the same as described.

I claim:

1. A liquid fuel injection nozzle unit comprising a body portion, a bore formed in the body portion, a valve member slidable within the bore, a seating defined in the bore, said valve member being shaped for co-operation with said seating, passage means through which fuel under pressure can be applied to said valve member to lift the valve member away from the seating to permit flow of fuel through an outlet, resilient means for urging the valve member into contact with the seating, a fluid pressure operable means operatively connected to said valve member, and a conduit through which fuel under pressure leaking between the valve member and the bore is applied to said means, so that the fuel under pressure acting on said means assists the action of the resilient means in closing the valve member onto the seating.

2. A nozzle unit as claimed in claim 1 in which said fluid pressure operable means defines a first surface against which the fuel under pressure can bear.

3. A nozzle unit as claimed in claim 2 in which said fluid pressure operable means defines a second surface which during closure of the valve displaces fluid, and means for controlling the rate of displacement of fluid to effect a control of the rate of movement of the valve member into contact with the seating.

4. A nozzle unit as claimed in claim 3 in which said means comprises an orifice.

5. A nozzle unit as claimed in claim 2 including valve means for controlling the pressure of fuel applied to said first surface.

6. A nozzle unit as claimed in claim 5 in which said fluid pressure operable means comprises a piston slidable within a cylinder, one end of the cylinder serving as an abutment for a spring forming said resilient means and an aperture in the other end of the cylinder and a push rod passing through the aperture to. extend between the piston and the valve member.

7. A nozzle unit as claimed in claim 6 in which the spring acts upon an end of the piston, said end of the piston defining said first surface.

8. A nozzle unit as claimed in claim 7'in which a space is defined about said push rod, said space receivsingle valve means for controlling the pressure of fuel applied to said first surfaces of the units. 

1. A liquid fuel injection nozzle unit comprising a body portion, a bore formed in the body portion, a valve member slidable within the bore, a seating defined in the bore, said valve member being shaped for co-operation with said seating, passage means through which fuel under pressure can be applied to said valve member to lift the valve member away from the seating to permit flow of fuel through an outlet, resilient means for urging the valve member into contact with the seating, a fluid pressure operable means operatively connected to said valve member, and a conduit through which fuel under pressure leaking between the valve member and the bore is applied to said means, so that the fuel under pressure acting on said means assists the action of the resilient means in closing the valve member onto the seating.
 2. A nozzle unit as claimed in claim 1 in which said fluid pressure operable means defines a first surface against which the fuel under pressure can bear.
 3. A nozzle unit as claimed in claim 2 in which said fluid pressure operable means defines a second surface which during closure of the valve displaces fluid, and means for controlling the rate of displacement of fluid to effect a control of the rate of movement of the valve member into contact with the seating.
 4. A nozzle unit as claimed in claim 3 in which said means comprises an orifice.
 5. A nozzle unit as claimed in claim 2 including valve means for controlling the pressure of fuel applied to said first surface.
 6. A nozzle unit as claimed in claim 5 in which said fluid pressure operable means comprises a piston slidable within a cylinder, one end of the cylinder serving as an abutment for a spring forming said resilient means and an aperture in the other end of the cylinder and a push rod passing through the aperture to extend between the piston and the valve member.
 7. A nozzle unit as claimed in claim 6 in which the spring acts upon an end of the piston, said end of the piston defining said first surface.
 8. A nozzle unit as claimed in claim 7 in which a space is defined about said push rod, said space receiving the fuel leaking past the valve member, said space communicating by way of a conduit, with said one end of the cylinder.
 9. A nozzle unit as claimed in claim 5 in which said fluid pressure operable means comprises a diaphragm.
 10. A liquid fuel injection system including a plurality of nozzle units as claimed in claim 4 and including a single valve means for controlling the pressure of fuel applied to said first surfaces of the units. 